Imaging atherosclerosis with positron emission tomography

Preclinical evaluation of an 18F-labeled Tenascin-C aptamer for PET imaging of atherosclerotic plaque in mouse models of atherosclerosis

Tenascin-C is an extracellular matrix glycoprotein strongly expressed in coronary atherosclerotic plaque. Aptamers are single-stranded oligonucleotides that bind to specific target molecules with high affinity. This study hypothesized that tenascin-C expression at atherosclerotic plaque in vivo could be detected by tenascin-C specific aptamers using positron emission tomography (PET). This paper reports the radiosynthesis of a fluorine-18 (18F)-labeled tenascin-C aptamer for the biodistribution and PET imaging of the tenascin-C expression in apolipoprotein E-deficient (ApoE-/-) mice. The aortas ApoE-/- mice showed significantly increased positive areas of Oil red O staining than control C57BL/6 mice, and tenascin-C expression was detected in foam cells accumulated in the subendothelial lesions of ApoE-/- mice. The ex vivo biodistribution of the 18F-labeled tenascin-C aptamer showed significantly increased uptake at the aorta of ApoE-/- mice, and ex vivo autoradiography of aorta revealed the high accumulation of the 18F-labeled tenascin-C aptamer in the atherosclerotic lesions of ApoE-/- mice, which was consistent with the location of the atherosclerotic plaques detected by Oil red O staining. PET imaging of the 18F-labeled tenascin-C aptamer revealed a significantly higher mean standardized uptake in the aorta of the ApoE-/- mice than the control C57BL/6 mice. These data highlight the potential use of tenascin-C aptamer to diagnose atherosclerotic lesions in vivo.

Activatable Probes for Ratiometric Imaging of Endogenous Biomarkers In Vivo

Dynamic variations in the concentration and abnormal distribution of endogenous biomarkers are strongly associated with multiple physiological and pathological states. Therefore, it is crucial to design imaging systems capable of real-time detection of dynamic changes in biomarkers for the accurate diagnosis and effective treatment of diseases. Recently, ratiometric imaging has emerged as a widely used technique for sensing and imaging of biomarkers due to its advantage of circumventing the limitations inherent to conventional intensity-dependent signal readout methods while also providing built-in self-calibration for signal correction. Here, the recent progress of ratiometric probes and their applications in sensing and imaging of biomarkers are outlined. Ratiometric probes are classified according to their imaging mechanisms, and ratiometric photoacoustic imaging, ratiometric optical imaging including photoluminescence imaging and self-luminescence imaging, ratiometric magnetic resonance imaging, and dual-modal ratiometric imaging are discussed. The applications of ratiometric probes in the sensing and imaging of biomarkers such as pH, reactive oxygen species (ROS), reactive nitrogen species (RNS), glutathione (GSH), gas molecules, enzymes, metal ions, and hypoxia are discussed in detail. Additionally, this Review presents an overview of challenges faced in this field along with future research directions.

Longitudinal imaging of murine atherosclerosis with 2-deoxy-2-[18F]fluoro-D-glucose and [18F]-sodium fluoride in genetically modified Apolipoprotein E knock-out and wild type mice

In a longitudinal design, four arterial segments in mice were followed by positron emission tomography/computed tomography (PET/CT) imaging. We aimed to determine how the tracers reflected the development of atherosclerosis via the uptake of 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) for imaging inflammation and [18F]-sodium fluoride (Na[18F]F) for imaging active microcalcification in a murine model of atherosclerosis. Apolipoprotein E knock-out (ApoE) mice and C57 BL/6NtaC (B6) mice were divided into four groups. They received either normal chow (N = 7, ApoE mice and N = 6, B6 mice) for 32 weeks or a high-fat diet (N = 6, ApoEHFD mice and N = 9, B6HFD mice) for 32 weeks. The mice were scanned with [18F]FDG and Na[18F]F using a dedicated small animal PET/CT scanner at three timepoints. The tracer uptakes in four aortic segments (abdominal aorta, aortic arch, ascending aorta, and thoracic aorta) were measured and reported as SUVmax values. The uptake of [18F]FDG (SUVmax: 5.7 ± 0.5 vs 1.9 ± 0.2, 230.3%, p =  < 0.0001) and Na[18F]F (SUVmax: 9.6 ± 1.8 vs 4.0 ± 0.3, 175%, p = 0.007) was significantly increased in the abdominal aorta of ApoEHFD mice at Week 32 compared to baseline abdominal aorta values of ApoEHFD mice. [18F]FDG uptake in the aortic arch, ascending aorta and the thoracic aorta of B6HFD mice at Week 32 showed a robust resemblance to the abdominal aorta uptake whereas the Na[18F]F uptake only resembled in the thoracic aorta of B6HFD mice at Week 32 compared to the abdominal aorta. The uptake of both [18F]FDG and Na[18F]F increased as the disease progressed over time, and the abdominal aorta provided a robust measure across mouse strain and diet. Therefore, it seems to be the preferred region for image readout. For [18F]FDG-PET, both B6 and ApoE mice provide valuable information and either mouse strain may be used in preclinical cardiovascular studies, whereas for Na[18F]F -PET, ApoE mice should be preferred.

Imaging in inflammatory arthritis: progress towards precision medicine

Imaging techniques such as ultrasonography and MRI have gained ground in the diagnosis and management of inflammatory arthritis, as these imaging modalities allow a sensitive assessment of musculoskeletal inflammation and damage. However, these techniques cannot discriminate between disease subsets and are currently unable to deliver an accurate prediction of disease progression and therapeutic response in individual patients. This major shortcoming of today's technology hinders a targeted and personalized patient management approach. Technological advances in the areas of high-resolution imaging (for example, high-resolution peripheral quantitative computed tomography and ultra-high field MRI), functional and molecular-based imaging (such as chemical exchange saturation transfer MRI, positron emission tomography, fluorescence optical imaging, optoacoustic imaging and contrast-enhanced ultrasonography) and artificial intelligence-based data analysis could help to tackle these challenges. These new imaging approaches offer detailed anatomical delineation and an in vivo and non-invasive evaluation of the immunometabolic status of inflammatory reactions, thereby facilitating an in-depth characterization of inflammation. By means of these developments, the aim of earlier diagnosis, enhanced monitoring and, ultimately, a personalized treatment strategy looms closer.

Exploring atherosclerosis imaging with contrast-enhanced MRI using PEGylated ultrasmall iron oxide nanoparticles

Plaque rupture is a critical concern due to its potential for severe outcomes such as cerebral infarction and myocardial infarction, underscoring the urgency of noninvasive early diagnosis. Magnetic resonance imaging (MRI) has gained prominence in plaque imaging, leveraging its noninvasiveness, high spatial resolution, and lack of ionizing radiation. Ultrasmall iron oxides, when modified with polyethylene glycol, exhibit prolonged blood circulation and passive targeting toward plaque sites, rendering them conducive for MRI. In this study, we synthesized ultrasmall iron oxide nanoparticles of approximately 3 nm via high-temperature thermal decomposition. Subsequent surface modification facilitated the creation of a dual-modality magnetic resonance/fluorescence probe. Upon intravenous administration of the probes, MRI assessment of atherosclerotic plaques and diagnostic evaluation were conducted. The application of Flash-3D sequence imaging revealed vascular constriction at lesion sites, accompanied by a gradual signal amplification postprobe injection. T1-weighted imaging of the carotid artery unveiled a progressive signal ratio increase between plaques and controls within 72 h post-administration. Fluorescence imaging of isolated carotid arteries exhibited incremental lesion-to-control signal ratios. Additionally, T1 imaging of the aorta demonstrated an evolving signal enhancement over 48 h. Therefore, the ultrasmall iron oxide nanoparticles hold immense promise for early and noninvasive diagnosis of plaques, providing an avenue for dynamic evaluation over an extended time frame.

Arterial wall inflammation assessed by 18F-FDG-PET/CT is higher in individuals with Type 1 diabetes and associated with circulating inflammatory proteins

AIMS

The article investigates whether chronic hyperglycaemia in Type 1 diabetes (T1D) is associated with a proinflammatory immune signature and with arterial wall inflammation, driving the development of atherosclerosis.

METHODS AND RESULTS

Patients with T1D (n = 41), and healthy age-, sex-, and body mass index-matched controls (n = 20) were recruited. Arterial wall inflammation and haematopoietic activity were measured with 2'-deoxy-2'-(18F)-fluoro-D-glucose (18F-FDG) positron emission tomography/computed tomography. In addition, flow cytometry of circulating leucocytes was performed as well as targeted proteomics to measure circulating inflammatory markers. 18F-FDG uptake in the wall of the abdominal aorta, carotid arteries, and iliac arteries was higher in T1D compared with that in the healthy controls. Also, 18F-FDG uptake in the bone marrow and spleen was higher in patients with T1D. CCR2 and CD36 expressions on circulating monocytes were higher in patients with T1D, as well as several circulating inflammatory proteins. In addition, several circulating inflammatory markers (osteoprotegerin, transforming growth factor-alpha, CX3CL1, and colony-stimulating factor-1) displayed a positive correlation with FDG uptake. Within T1D, no differences were found between people with a high and low HbA1c.

CONCLUSION

These findings strengthen the concept that chronic hyperglycaemia in T1D induces inflammatory changes that fuel arterial wall inflammation leading to atherosclerosis. The degree of hyperglycaemia appears to play a minor role in driving this inflammatory response in patients with T1D.

Anti-inflammatory effect of biologic therapy in patients with psoriatic disease: A prospective cohort FDG PET study

AIM

The aim of the study was to evaluate the changes in central vascular inflammation measured by FDG PET and myocardial blood flow reserve (MFR) determined by 82Rb PET following therapy with biologic agents for 6 months in patients with psoriatic arthritis (PsA) and/or cutaneous psoriasis (PsO) (group 1) and compare with PsO subjects receiving non-biologic therapy (group 2) and controls (group 3).

METHODS AND RESULTS

Target-to-background ratio (TBR) by FDG PET in the most diseased segment of the ascending aorta (TBRmax) was measured to assess vascular inflammation. 82Rb PET studies were used to assess changes in left ventricular MFR. A total of 34 participants were enrolled in the study (11 in group 1, 13 in group 2, and 10 controls). A significant drop in the thoracic aorta uptake was observed in the biologic-treated group (ΔTBRmax: - .46 ± .55) compared to the PsO group treated with non-biologic therapy (ΔTBRmax: .23 ± .67). Those showing response to biologic agents maintained MFR compared to who showed no response.

CONCLUSION

In a cohort of psoriasis patients treated with biologics, FDG uptake in the thoracic aorta decreased over the study period. Patients who demonstrated a significant anti-inflammatory response on FDG PET imaging maintained their MFR compared to non-responders.

Pyruvate dehydrogenase kinase regulates vascular inflammation in atherosclerosis and increases cardiovascular risk

AIMS

Recent studies have revealed a close connection between cellular metabolism and the chronic inflammatory process of atherosclerosis. While the link between systemic metabolism and atherosclerosis is well established, the implications of altered metabolism in the artery wall are less understood. Pyruvate dehydrogenase kinase (PDK)-dependent inhibition of pyruvate dehydrogenase (PDH) has been identified as a major metabolic step regulating inflammation. Whether the PDK/PDH axis plays a role in vascular inflammation and atherosclerotic cardiovascular disease remains unclear.

METHODS AND RESULTS

Gene profiling of human atherosclerotic plaques revealed a strong correlation between PDK1 and PDK4 transcript levels and the expression of pro-inflammatory and destabilizing genes. Remarkably, the PDK1 and PDK4 expression correlated with a more vulnerable plaque phenotype, and PDK1 expression was found to predict future major adverse cardiovascular events. Using the small-molecule PDK inhibitor dichloroacetate (DCA) that restores arterial PDH activity, we demonstrated that the PDK/PDH axis is a major immunometabolic pathway, regulating immune cell polarization, plaque development, and fibrous cap formation in Apoe-/- mice. Surprisingly, we discovered that DCA regulates succinate release and mitigates its GPR91-dependent signals promoting NLRP3 inflammasome activation and IL-1β secretion by macrophages in the plaque.

CONCLUSIONS

We have demonstrated for the first time that the PDK/PDH axis is associated with vascular inflammation in humans and particularly that the PDK1 isozyme is associated with more severe disease and could predict secondary cardiovascular events. Moreover, we demonstrate that targeting the PDK/PDH axis with DCA skews the immune system, inhibits vascular inflammation and atherogenesis, and promotes plaque stability features in Apoe-/- mice. These results point toward a promising treatment to combat atherosclerosis.

The Presence of Residual Vascular and Adipose Tissue Inflammation on 18F-FDG PET in Patients with Chronic Coronary Artery Disease

Purpose

We evaluated the residual vascular and adipose tissue inflammation in patients with chronic coronary artery disease (CAD) using positron emission tomography (PET).

Methods

Our study population consisted of 98 patients with known CAD and 94 control subjects who had undergone 18F-fluorodeoxyglucose (18F-FDG) PET due to non-cardiac reasons. Aortic root and vena cava superior 18F-FDG uptake were measured to obtain the aortic root target-to-background ratio (TBR). In addition, adipose tissue PET measurements were done in pericoronary, epicardial, subcutaneous, and thoracic adipose tissue. Adipose tissue TBR was calculated using the left atrium as a reference region. Data are presented as mean ± standard deviation or as median (interquartile range).

Results

The aortic root TBR was higher in CAD patients compared to control subjects, 1.68 (1.55-1.81) vs. 1.53 (1.43-1.64), p < 0.001. Subcutaneous adipose tissue uptake was elevated in CAD patients 0.30 (0.24-0.35) vs. 0.27 (0.23-0.31), p < 0.001. Metabolic activity of CAD patients and control subjects was comparable in the pericoronary (0.81 ± 0.18 vs. 0.80 ± 0.16, p = 0.59), epicardial (0.53 ± 0.21 vs. 0.51 ± 0.18, p = 0.38) and thoracic (0.31 ± 0.12 vs. 0.28 ± 0.12, p = 0.21) adipose tissue regions. Aortic root or adipose tissue 18F-FDG uptake was not associated with the common CAD risk factors, coronary calcium score, or aortic calcium score (p value > 0.05).

Conclusion

Patients with a chronic CAD had a higher aortic root and subcutaneous adipose tissue 18F-FDG uptake compared to control patients, which suggests residual inflammatory risk.

Complex Interplay Between Metabolism and CD4+ T-Cell Activation, Differentiation, and Function: a Novel Perspective for Atherosclerosis Immunotherapy

Atherosclerosis is a complex pathological process that results from the chronic inflammatory reaction of the blood vessel wall and involves various immune cells and cytokines. An imbalance in the proportion and function of the effector CD4⁺ T-cell (Teff) and regulatory T-cell (Treg) subsets is an important cause of the occurrence and development of atherosclerotic plaques. Teff cells depend on glycolytic metabolism and glutamine catabolic metabolism for energy, while Treg cells mainly rely on fatty acid oxidation (FAO), which is crucial for determining the fate of CD4⁺ T cells during differentiation and maintaining their respective immune functions. Here, we review recent research achievements in the field of immunometabolism related to CD4⁺ T cells, focusing on the cellular metabolic pathways and metabolic reprogramming involved in the activation, proliferation, and differentiation of CD4⁺ T cells. Subsequently, we discuss the important roles of mTOR and AMPK signaling in regulating CD4⁺ T-cell differentiation. Finally, we evaluated the links between CD4⁺ T-cell metabolism and atherosclerosis, highlighting the potential of targeted modulation of CD4⁺ T-cell metabolism in the prevention and treatment of atherosclerosis in the future.

Reducing cardiovascular risk with immunomodulators: a randomised active comparator trial among patients with rheumatoid arthritis

OBJECTIVE

Recent large-scale randomised trials demonstrate that immunomodulators reduce cardiovascular (CV) events among the general population. However, it is uncertain whether these effects apply to rheumatoid arthritis (RA) and if certain treatment strategies in RA reduce CV risk to a greater extent.

METHODS

Patients with active RA despite use of methotrexate were randomly assigned to addition of a tumour necrosis factor (TNF) inhibitor (TNFi) or addition of sulfasalazine and hydroxychloroquine (triple therapy) for 24 weeks. Baseline and follow-up 18F-fluorodeoxyglucose-positron emission tomography/CT scans were assessed for change in arterial inflammation, an index of CV risk, measured as an arterial target-to-background ratio (TBR) in the carotid arteries and aorta.

RESULTS

115 patients completed the protocol. The two treatment groups were well balanced with a median age of 58 years, 71% women, 57% seropositive and a baseline disease activity score in 28 joints of 4.8 (IQR 4.0, 5.6). Baseline TBR was similar across the two groups. Significant TBR reductions were observed in both groups-ΔTNFi: -0.24 (SD=0.51), Δtriple therapy: -0.19 (SD=0.51)-without difference between groups (difference in Δs: -0.02, 95% CI -0.19 to 0.15, p=0.79). While disease activity was significantly reduced across both treatment groups, there was no association with change in TBR (β=0.04, 95% CI -0.03 to 0.10).

CONCLUSION

We found that addition of either a TNFi or triple therapy resulted in clinically important improvements in vascular inflammation. However, the addition of a TNFi did not reduce arterial inflammation more than triple therapy.

TRIAL REGISTRATION NUMBER

NCT02374021.

Molecularly targeted nanomedicine enabled by inorganic nanoparticles for atherosclerosis diagnosis and treatment

Atherosclerosis, a chronic cardiovascular disease caused by plaque development in arteries, remains a leading cause of morbidity and mortality. Atherosclerotic plaques are characterized by the expression and regulation of key molecules such as cell surface receptors, cytokines, and signaling pathway proteins, potentially facilitating precise diagnosis and treatment on a molecular level by specifically targeting the characteristic molecules. In this review, we highlight the recent progress in the past five years on developing molecularly targeted nanomedicine for imaging detection and treatment of atherosclerosis with the use of inorganic nanoparticles. Through targeted delivery of imaging contrast nanoparticles to specific molecules in atherogenesis, atherosclerotic plaque development at different stages could be identified and monitored via various molecular imaging modalities. We also review molecularly targeted therapeutic approaches that target and regulate molecules associated with lipid regulation, inflammation, and apoptosis. The review is concluded with discussion on current challenges and future development of nanomedicine for atherosclerotic diagnosis and treatment.

Multimodality Imaging in the Detection of Ischemic Heart Disease in Women

Women with coronary artery disease tend to have a worse short and long-term prognosis relative to men and the incidence of atherosclerotic cardiovascular disease is increasing. Women are less likely to present with classic anginal symptoms when compared with men and more likely to be misdiagnosed. Several non-invasive imaging modalities are available for diagnosing ischemic heart disease in women and many of these modalities can also assist with prognostication and help to guide management. Selection of the optimal imaging modality to evaluate women with possible ischemic heart disease is a scenario which clinicians often encounter. Earlier modalities such as exercise treadmill testing demonstrate significant performance variation in men and women, while newer modalities such as coronary CT angiography, myocardial perfusion imaging and cardiac magnetic resonance imaging are highly specific and sensitive for the detection of ischemia and coronary artery disease with greater parity between sexes. Individual factors, availability, diagnostic performance, and female-specific considerations such as pregnancy status may influence the decision to select one modality over another. Emerging techniques such as strain rate imaging, CT-myocardial perfusion imaging and cardiac magnetic resonance imaging present additional options for diagnosing ischemia and coronary microvascular dysfunction.

Unravelling the role of macrophages in cardiovascular inflammation through imaging: a state-of-the-art review

Cardiovascular disease remains the leading cause of death and disability for patients across the world. Our understanding of atherosclerosis as a primary cholesterol issue has diversified, with a significant dysregulated inflammatory component that largely remains untreated and continues to drive persistent cardiovascular risk. Macrophages are central to atherosclerotic inflammation, and they exist along a functional spectrum between pro-inflammatory and anti-inflammatory extremes. Recent clinical trials have demonstrated a reduction in major cardiovascular events with some, but not all, anti-inflammatory therapies. The recent addition of colchicine to societal guidelines for the prevention of recurrent cardiovascular events in high-risk patients with chronic coronary syndromes highlights the real-world utility of this class of therapies. A highly targeted approach to modification of interleukin-1-dependent pathways shows promise with several novel agents in development, although excessive immunosuppression and resulting serious infection have proven a barrier to implementation into clinical practice. Current risk stratification tools to identify high-risk patients for secondary prevention are either inadequately robust or prohibitively expensive and invasive. A non-invasive and relatively inexpensive method to identify patients who will benefit most from novel anti-inflammatory therapies is required, a role likely to be fulfilled by functional imaging methods. This review article outlines our current understanding of the inflammatory biology of atherosclerosis, upcoming therapies and recent landmark clinical trials, imaging modalities (both invasive and non-invasive) and the current landscape surrounding functional imaging including through targeted nuclear and nanobody tracer development and their application.

Radiopharmaceuticals for PET and SPECT Imaging: A Literature Review over the Last Decade

Positron emission tomography (PET) uses radioactive tracers and enables the functional imaging of several metabolic processes, blood flow measurements, regional chemical composition, and/or chemical absorption. Depending on the targeted processes within the living organism, different tracers are used for various medical conditions, such as cancer, particular brain pathologies, cardiac events, and bone lesions, where the most commonly used tracers are radiolabeled with 18F (e.g., [¹⁸F]-FDG and NA [¹⁸F]). Oxygen-15 isotope is mostly involved in blood flow measurements, whereas a wide array of ¹¹C-based compounds have also been developed for neuronal disorders according to the affected neuroreceptors, prostate cancer, and lung carcinomas. In contrast, the single-photon emission computed tomography (SPECT) technique uses gamma-emitting radioisotopes and can be used to diagnose strokes, seizures, bone illnesses, and infections by gauging the blood flow and radio distribution within tissues and organs. The radioisotopes typically used in SPECT imaging are iodine-123, technetium-99m, xenon-133, thallium-201, and indium-111. This systematic review article aims to clarify and disseminate the available scientific literature focused on PET/SPECT radiotracers and to provide an overview of the conducted research within the past decade, with an additional focus on the novel radiopharmaceuticals developed for medical imaging.

Molecular imaging in atherosclerosis

Purpose

As atherosclerosis is a  prominent cause of morbidity and mortality, early detection of atherosclerotic plaques is vital to prevent complications. Imaging plays a significant role in this goal. Molecular imaging and structural imaging detect different phases of atherosclerotic progression. In this review, we explain the relation between these types of imaging with the physiopathology of plaques, along with their advantages and disadvantages. We also discuss in detail the most commonly used positron emission tomography (PET) radiotracers for atherosclerosis imaging.

Method

A comprehensive search was conducted to extract articles related to imaging of atherosclerosis in PubMed, Google Scholar, and Web of Science. The obtained papers were reviewed regarding precise relation with our topic. Among the search keywords utilized were "atherosclerosis imaging", "atherosclerosis structural imaging", "atherosclerosis CT scan" "positron emission tomography", "PET imaging", "18F-NaF", "18F-FDG", and "atherosclerosis calcification."

Result

Although structural imaging such as computed tomography (CT) offers essential information regarding plaque structure and morphologic features, these modalities can only detect macroscopic alterations that occur later in the disease’s progression, when the changes are frequently irreversible. Molecular imaging modalities like PET, on the other hand, have the advantage of detecting microscopic changes and allow us to treat these plaques before irreversible changes occur. The two most commonly used tracers in PET imaging of atherosclerosis are 18F-sodium fluoride (18F-NaF) and 18F-fluorodeoxyglucose (18F-FDG). While there are limitations in the use of 18F-FDG for the detection of atherosclerosis in coronary arteries due to physiological uptake in myocardium and high luminal blood pool activity of 18F-FDG, 18F-NaF PET is less affected and can be utilized to analyze the coronary arteries in addition to the peripheral vasculature.

Conclusion

Molecular imaging with PET/CT has become a useful tool in the early detection of atherosclerosis. 18F-NaF PET/CT shows promise in the early global assessment of atherosclerosis, but further prospective studies are needed to confirm its role in this area.

Characterizing the transition from immune response to tissue repair after myocardial infarction by multiparametric imaging

Persistent inflammation following myocardial infarction (MI) precipitates adverse outcome including acute ventricular rupture and chronic heart failure. Molecular imaging allows longitudinal assessment of immune cell activity in the infarct territory and predicts severity of remodeling. We utilized a multiparametric imaging platform to assess the immune response and cardiac healing following MI in mice. Suppression of circulating macrophages prior to MI paradoxically resulted in higher total leukocyte content in the heart, demonstrated by increased CXC motif chemokine receptor 4 (CXCR4) positron emission tomography imaging. This supported the formation of a thrombus overlying the injured region, as identified by magnetic resonance imaging. The injured and thrombotic region in macrophage depeleted mice subsequently showed active calcification, as evidenced by accumulation of ¹⁸F-fluoride and by cardiac computed tomography. Importantly, macrophage suppression triggered a prolonged inflammatory response confirmed by post-mortem tissue analysis that was associated with higher mortality from ventricular rupture early after occlusion and with increased infarct size and worse chronic contractile function at 6 weeks after reperfusion. These findings establish a molecular imaging toolbox for monitoring the interplay between adverse immune response and tissue repair after MI. This may serve as a foundation for development and monitoring of novel targeted therapies that may include immune modulation and endogenous healing support.

Re-engineered imaging agent using biomimetic approaches

Recent progress in biomedical technology, the clinical bioimaging, has a greater impact on the diagnosis, treatment, and prevention of disease, especially by early intervention and precise therapy. Varieties of organic and inorganic materials either in the form of small molecules or nano-sized materials have been engineered as a contrast agent (CA) to enhance image resolution among different tissues for the detection of abnormalities such as cancer and vascular occlusion. Among different innovative imaging agents, contrast agents coupled with biologically derived endogenous platform shows the promising application in the biomedical field, including drug delivery and bioimaging. Strategy using biocomponents such as cells or products of cells as a delivery system predominantly reduces the toxic behavior of its cargo, as these systems reduce non-specific distribution by navigating its cargo toward the targeted location. The hypothesis is that depending on the original biological role of the naïve cell, the contrast agents carried by such a system can provide corresponding natural designated behavior. Therefore, by combining properties of conventional synthetic molecules and nanomaterials with endogenous cell body, new solutions in the field of bioimaging to overcome biological barriers have been offered as innovative bioengineering. In this review, we will discuss the engineering of cell and cell-derived components as a delivery system for various contrast agents to achieve clinically relevant contrast for diagnosis and study underlining mechanism of disease progression. This article is categorized under: Nanotechnology Approaches to Biology > Cells at the Nanoscale Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Metabolic Activity of Visceral Adipose Tissue Is Associated with Metastatic Status of Lymph Nodes in Endometrial Cancer: A 18F-FDG PET/CT Study

Obesity contributes to increased cancer incidence and aggressiveness in patients with endometrial cancer. Inflamed metabolic activity of visceral adipose tissue (VAT) is regarded as a key underlying mechanism of adverse consequences of obesity. The aim of this study was to investigate the association between inflammatory metabolic activity of VAT evaluated by ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) and metastatic status of lymph nodes (LN) in patients with endometrial cancer. In total, 161 women with newly diagnosed endometrial cancer, who received preoperative 18F-FDG PET/CT, were enrolled. VAT inflammatory metabolic activity was defined as V/S ratio and measured from the maximum standardized uptake value (SUVmax) of VAT normalized to the SUVmax of subcutaneous adipose tissue (SAT). The positive LN metastasis group exhibited a significantly higher V/S ratio than the negative LN metastasis group. Systemic inflammatory surrogate markers including high sensitivity C-reactive protein, spleen SUVmax, and bone marrow SUVmax were also higher in the LN metastasis group than in the negative LN metastasis group, showing significant correlations with V/S ratio. In multivariate logistic regression analysis, V/S ratio was independently associated with LN metastasis. V/S ratio is independently associated with the LN metastasis status in patients with endometrial cancer. This finding could be useful as a potential surrogate marker of obesity-induced VAT inflammation associated with tumor aggressiveness.

Advances in Radiopharmaceutical Sciences for Vascular Inflammation Imaging: Focus on Clinical Applications

Biomedical imaging technologies offer identification of several anatomic and molecular features of disease pathogenesis. Molecular imaging techniques to assess cellular processes in vivo have been useful in advancing our understanding of several vascular inflammatory diseases. For the non-invasive molecular imaging of vascular inflammation, nuclear medicine constitutes one of the best imaging modalities, thanks to its high sensitivity for the detection of probes in tissues. 2-[¹⁸F]fluoro-2-deoxy-d-glucose ([¹⁸F]FDG) is currently the most widely used radiopharmaceutical for molecular imaging of vascular inflammatory diseases such as atherosclerosis and large-vessel vasculitis. The combination of [¹⁸F]FDG and positron emission tomography (PET) imaging has become a powerful tool to identify and monitor non-invasively inflammatory activities over time but suffers from several limitations including a lack of specificity and avid background in different localizations. The use of novel radiotracers may help to better understand the underlying pathophysiological processes and overcome some limitations of [¹⁸F]FDG PET for the imaging of vascular inflammation. This review examines how [¹⁸F]FDG PET has given us deeper insight into the role of inflammation in different vascular pathologies progression and discusses perspectives for alternative radiopharmaceuticals that could provide a more specific and simple identification of pathologies where vascular inflammation is implicated. Use of these novel PET tracers could lead to a better understanding of underlying disease mechanisms and help inform the identification and stratification of patients for newly emerging immune-modulatory therapies. Future research is needed to realize the true clinical translational value of PET imaging in vascular inflammatory diseases.

Clinical Molecular Imaging for Atherosclerotic Plaque

Atherosclerosis is a well-known disease leading to cardiovascular events, including myocardial infarction and ischemic stroke. These conditions lead to a high mortality rate, which explains the interest in their prevention, early detection, and treatment. Molecular imaging is able to shed light on the basic pathophysiological processes, such as inflammation, that cause the progression and instability of plaque. The most common radiotracers used in clinical practice can detect increased energy metabolism (FDG), macrophage number (somatostatin receptor imaging), the intensity of cell proliferation in the area (labeled choline), and microcalcifications (fluoride imaging). These radiopharmaceuticals, especially FDG and labeled sodium fluoride, can predict cardiovascular events. The limitations of molecular imaging in atherosclerosis include low uptake of highly specific tracers, possible overlap with other diseases of the vessel wall, and specific features of certain tracers’ physiological distribution. A common protocol for patient preparation, data acquisition, and quantification is needed in the area of atherosclerosis imaging research.

Imaging Inflammation in Patients and Animals: Focus on PET Imaging the Vulnerable Plaque

Acute coronary syndrome (ACS) describes a range of conditions associated with the rupture of high-risk or vulnerable plaque. Vulnerable atherosclerotic plaque is associated with many changes in its microenvironment which could potentially cause rapid plaque progression. Present-day PET imaging presents a plethora of radiopharmaceuticals designed to image different characteristics throughout plaque progression. Improved knowledge of atherosclerotic disease pathways has facilitated a growing number of pathophysiological targets for more innovative radiotracer design aimed at identifying at-risk vulnerable plaque and earlier intervention opportunity. This paper reviews the efficacy of PET imaging radiotracers ¹⁸F-FDG, ¹⁸F-NaF, ⁶⁸Ga-DOTATATE, ⁶⁴Cu-DOTATATE and ⁶⁸Ga-pentixafor in plaque characterisation and risk assessment, as well as the translational potential of novel radiotracers in animal studies. Finally, we discuss our murine PET imaging experience and the challenges encountered.

New insight into biology, molecular diagnostics and treatment options of unstable carotid atherosclerotic plaque: a narrative review

Indications for intervention in hemodynamically relevant carotid artery stenosis (carotid endarterectomy or stenting) are primarily based on a degree of stenosis and symptomatology. To date the plaque vulnerability is rarely taken into account in clinical decision making although development of molecular imaging allows a better understanding of plaque biology and provides new techniques detecting potentially vulnerable plaque at risk. A significant number of reports describing the mechanisms of unstable plaque formation suggest that it is a multifactorial process. Inflammation, lipid accumulation, apoptosis, proteolysis, the thrombotic process and angiogenesis are among the main factors of carotid plaque destabilization. Although inflammation is a key process in development of plaque vulnerability, the hemostasis and neoangiogenesis should be regarded as equally important. Only a small group of asymptomatic patients may benefit from the invasive treatment and it remains a challenge to determine whether initially asymptomatic carotid plaque become unstable or vulnerable. Currently, the main task of research on atherosclerotic lesion imaging is focused on functional state of the plaque. The presence of one or more features such as stenosis progression, large plaque area, large juxta-luminal black area, plaque echolucency, intra-plaque hemorrhage, impaired cerebral vascular reserve and spontaneous embolization may indicate patients at higher risk for stroke suitable for revascularization. Treatment of carotid stenosis as one of the manifestations of generalized atherosclerosis requires a broad approach. Nowadays pharmacological treatment options for the atherosclerotic process are largely aimed at stimulating the plaque stabilization, but in symptomatic patients and selected asymptomatic patients, carotid plaque should be removed as a potential source of embolism.

Myocardial Glucose Metabolism Is Increased in Newly Diagnosed Lung Adenocarcinoma

BACKGROUND

Cardiac metabolism alterations may be involved in abnormalities of cancer patients' cardiovascular system. This study aimed to explore whether left ventricular myocardial glucose metabolism is altered and its related factors in newly diagnosed patients with lung adenocarcinoma (LAD) who underwent fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT).

METHODS

From our 18F-FDG PET/CT imaging database, 171 patients with newly diagnosed LAD and 43 nononcologic subjects with matched age and sex were retrospectively analyzed. The included patients underwent conventional 18F-FDG PET/CT imaging with a >12-h fasting before 18F-FDG administration. The standardized uptake values (SUVs) of the left ventricular (LV) myocardium, arterial wall, epicardial adipose tissue (EAT), spleen, and bone marrow were separately measured. Laboratory parameters and echocardiographic results were collected as well. LAD patients were divided into 2 groups based on the 95th percentile of LV maximal SUV (SUVmax) obtained from the 43 nononcologic subjects. Univariate analysis and multiple logistic regression analysis were used to identify significant factors.

RESULTS

Higher LV SUVmax was found (3.8 [2.4, 7.7] vs. 3.0 [2.0, 5.4], p = 0.052) in LAD than that in nononcologic patients, whereas no significant differences of 18F-FDG uptake were found in the arterial wall, EAT, spleen, or bone marrow between LAD patients and controls. The maximum diameter (Dmax) of the LAD lesion, SUVmax of spleen, and SUVmax of EAT were related to LV SUVmax in LAD.

CONCLUSIONS

Myocardial glucose metabolism is increased in patients with newly diagnosed LAD. Dmax of LAD lesion, spleen activity, and EAT activity contribute to the increased LV activity in LAD.

Multimodality molecular imaging: Gaining insights into the mechanisms linking chronic stress to cardiovascular disease

Positron emission tomography (PET) imaging can yield unique mechanistic insights into the pathophysiology of atherosclerosis. 18F-fluorodeoxyglucose (18F-FDG), a radiolabeled glucose analog, is retained by cells in proportion to their glycolytic activity. While 18F-FDG accumulates within several cell types in the arterial wall, its retention correlates with macrophage content, providing an index of arterial inflammation (ArtI) which predicts subsequent cardiovascular disease (CVD) events. Furthermore, 18F-FDG-PET imaging allows the simultaneous assessment of metabolic activity in several tissues (e.g., brain, bone marrow) and is performed in conjunction with cross-sectional imaging that enables multi-organ structural assessments. Accordingly, 18F-FDG-PET/computed tomography (CT) imaging facilitates evaluation of disease pathways that span multiple organ systems. Within this paradigm, 18F-FDG-PET/CT imaging has been implemented to study the mechanism linking chronic stress to CVD. To evaluate this, stress-associated neural activity can be quantified (as metabolic activity of the amygdala (AmygA)), while leukopoietic activity, ArtI, and coronary plaque burden are assessed concurrently. Such simultaneous quantification of tissue structures and activities enables the evaluation of multi-organ pathways with the aid of mediation analysis. Using this approach, multi-system 18F-FDG-PET/CT imaging studies have demonstrated that chronically heightened stress-associated neurobiological activity promotes leukopoietic activity and systemic inflammation. This in turn fuels more ArtI and greater non-calcified coronary plaque burden, which result in more CVD events. Subsequent studies have revealed that common stressors, such as chronic noise exposure and income disparities, drive the front end of this pathway to increase CVD risk. Hence, multi-tissue multimodality imaging serves as a powerful tool to uncover complex disease mechanisms.

Series of myocardial FDG uptake requiring considerations of myocardial abnormalities in FDG-PET/CT

Distinct from cardiac PET performed with preparation to control physiological FDG uptake in the myocardium, standard FDG-PET/CT performed with 4-6 h of fasting will show variation in myocardial FDG uptake. For this reason, important signs of myocardial and pericardial abnormality revealed by myocardial FDG uptake tend to be overlooked. However, recognition of possible underlying disease will support further patient management to avoid complications due to the disease. This review demonstrates the mechanism of FDG uptake in the myocardium, discusses the factors affecting uptake, and provides notable image findings that may suggest underlying disease.

Brief Report: Lower Socioeconomic Status Associates With Greater Systemic and Arterial Inflammation in HIV

OBJECTIVES

In the general population, the lower socioeconomic status (SES) associates with greater systemic and arterial inflammation and a greater risk of cardiovascular disease. Because arterial inflammation is heightened in individuals living with HIV, we tested the hypothesis that SES associates with arterial inflammation in this population.

SETTINGS

Prospective cohort study.

METHODS

Men living with HIV were recruited. Arterial inflammation and leukopoietic activity (ie, bone marrow activity) were measured using 18F-fluorodeoxyglucose positron emission tomography/computed tomography. Zip code-level SES measures were derived from the US Census Bureau. Linear regression and mediation analyses were used to assess associations between SES, arterial inflammation, leukopoietic activity, C-reactive protein (CRP), and interleukin-6.

RESULTS

Thirty-nine virologically suppressed men living with HIV were studied (mean ± SD age 50.5 ± 11.1 years). The median CD4 count was 663 cells/mm3 (interquartile range: 399-922); 82% were receiving antiretroviral therapies. Local median income inversely associated with arterial inflammation [standardized β (95% confidence interval): -0.42 (-0.76 to -0.08)] after adjusting for age, Framingham risk score, statin use, antiretroviral use, and nadir CD4 count. The high-school graduation rate independently associated with arterial inflammation [-0.45 (-0.78 to -0.12)] and CRP [-0.49 (-0.86 to -0.012)]. Mediation analysis demonstrated the impact of SES on arterial inflammation was partially mediated by heightened circulating inflammatory levels: ↓SES (as high school graduation rate) →↑CRP →↑arterial inflammation accounting for 44% of the total effect (P < 0.05).

CONCLUSION

In individuals living with HIV, lower SES independently associated with higher leukopoietic activity, circulating markers of inflammation, and arterial inflammation. Furthermore, the link between SES and arterial inflammation was mediated by increased systemic inflammation.

Association of Inflammatory Metabolic Activity of Psoas Muscle and Acute Myocardial Infarction: A Preliminary Observational Study with 18F-FDG PET/CT

Inflamed skeletal muscle promotes chronic inflammation in atherosclerotic plaques, thereby contributing to the increased risk of coronary artery disease (CAD). In this study, we evaluated the metabolic activity of psoas muscle, using ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT), and its association with carotid artery inflammation and acute myocardial infarction (AMI). In total, 90 participants (32 AMI, 33 chronic stable angina (CSA), and 25 control) were enrolled in this prospective study. Metabolic activity of skeletal muscle (SM) was measured by using maximum standardized uptake value (SUVmax) of psoas muscle, and corresponding psoas muscle area (SM area) was also measured. Carotid artery inflammation was evaluated by using the target-to background ratio (TBR) of carotid artery. SM SUVmax was highest in AMI, intermediate in CSA, and lowest in control group. SM SUVmax was significantly correlated with carotid artery TBR and systemic inflammatory surrogate markers. Furthermore, SM SUVmax was independently associated with carotid artery TBR and showed better predictability than SM area for the prediction of AMI. Metabolic activity of psoas muscle assessed by ¹⁸F-FDG PET/CT was associated with coronary plaque vulnerability and synchronized with the carotid artery inflammation in the participants with CAD. Furthermore, it may also be useful to predict AMI.

Association of neutrophil-to-lymphocyte ratio with non-calcified coronary artery burden in psoriasis: Findings from an observational cohort study

BACKGROUND

Inflammation in the form of elevated high-sensitivity c-reactive protein (hs-CRP) has been shown to be critical in the development of atherothrombosis. Psoriasis, a chronic inflammatory skin disease, is associated with high systemic-inflammation, elevated neutrophil-to-lymphocyte ratio (NLR) and accelerated non-calcified coronary artery burden (NCB) by coronary computed tomography angiography (CCTA). We hypothesized that NLR would associate with early, rupture-prone atherosclerosis assessed as NCB independent of hs-CRP.

METHODS

316 consecutive psoriasis participants were recruited with 233 having one-year follow-up as part of a prospective, observational cohort study design. CCTA scans were performed to assess NCB in all three major epicardial coronary arteries.

RESULTS

Patients with above average NLR (>mean: 2.29 ​± ​1.21) were older (mean ​± ​SD; 52.0 ​± ​12.8 vs. 47.9 ​± ​12.6, p ​= ​0.002), had higher hs-CRP (med. IQR: 2.3 (0.9-7.3) vs. 1.4 (0.7-3.2), p ​= ​0.001) and had higher NCB (mean ​± ​SD; 1.21 ​± ​0.58 vs. 1.13 ​± ​0.49, p ​= ​0.018) when compared to patients with below average NLR. NLR associated with psoriasis area severity index score (β ​= ​0.14, p ​= ​0.017), hs-CRP (β ​= ​0.16, p ​= ​0.005), as well as NCB independent of traditional risk factors, body mass index, statin use and hs-CRP (β ​= ​0.08, p ​= ​0.009). One year of biologic therapy for psoriasis was associated with a reduction in NLR (-14.5%, p ​< ​0.001), and this change in NLR associated with change in NCB in fully adjusted models and beyond hs-CRP (β ​= ​0.17, p ​= ​0.002).

CONCLUSION

NLR associated with psoriasis severity, hs-CRP and NCB at baseline. Biologic therapy reduced NLR over time and this change in NLR associated with the change in NCB at one-year. Taken together, these findings suggest that NLR may capture psoriasis patients at higher risk of NCB due to residual inflammation not fully captured by hs-CRP.

PTPN2 negatively regulates macrophage inflammation in atherosclerosis

Atherosclerosis is the main cause of cardiovascular disease. Systemic inflammation is one important characteristic in atherosclerosis. Pro-inflammatory macrophages can secrete inflammatory factors and promote the inflammation of atherosclerosis. It has a great value for the treatment of atherosclerosis by inhibiting the release of inflammatory factors in macrophages. However, the detailed mechanism of this process is still unclear. In this study, we constructed an APOE^-/- mice model of atherosclerosis to research the molecular mechanism of atherosclerosis. Protein tyrosine phosphatase non-receptor type 2 (PTPN2), an anti-inflammatory gene, was dramatically decreased in inflammatory mice. Deletion of PTPN2 could significantly induce monocytes toward M1 phenotype of macrophages, enhance the secretion of IL-12 and IL-1, and promote cell proliferation, invasion and metastasis. Mechanism research showed that PTPN2-mediated p65/p38/STAT3 de-phosphorylation could block the process of macrophage inflammation. In vivo experiments showed that PTPN2 may effectively inhibit the inflammatory response during atherosclerosis. In conclusion, we uncovered the negative role of PTPN2 in the occurrence of atherosclerosis, and this study provides a new potential target for atherosclerosis treatment.

The ability of Micropure® ultrasound technique to identify microcalcifications in carotid plaques

OBJECTIVES

To study the ability of Micropure® ultrasound technique to identify microcalcifications in carotid plaques.

METHODS

Forty-four carotids in 22 patients were enrolled in this study and were detected by routine ultrasound examination and Micropure® examination at the same time to identify microcalcifications in plaques. The results were compared with the tissue-background ratio (TBR) in ¹⁸F-NaF PET-CT imaging, which was performed one or two days after the ultrasound examination.

RESULTS

In the 44 carotids, plaques were detected in 37 carotids. Microcalcifications were detected by the Micropure® technique in 32 carotids, which were located surrounded by macrocalcifications in 23 carotids, in the fibre cap in 12 carotids, and in the base of the plaque in 6 carotids. Microcalcifications were not detected in 12 carotids. In ¹⁸F-NaF PET-CT examination, TBR > 1.61 (range 1.62-3.99, mean 2.25 ± 0.58) was detected in 37 carotids, and TBR < 1.61 was detected in 7 carotids. There were no significant differences between the two methods in detecting microcalcifications (p = 0.180). The sensitivity of the Micropure® technique in detecting microcalcifications was 81.08 %, and the specificity was 71.43 %.

CONCLUSIONS

Microcalcifications in the carotid artery detected by the Micropure® technique were well in accordance with ¹⁸F-NaF PET-CT scanning, with better sensitivity and specificity.

Association of glucose uptake of visceral fat and acute myocardial infarction: a pilot 18F-FDG PET/CT study

Background

Inflamed visceral adipose tissue (VAT) facilitates chronic inflammation in atherosclerotic lesions thereby leading to increased risk of coronary artery disease (CAD). In this study, we evaluated the glucose uptake of VAT and the carotid artery with ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET/CT) and their association with CAD, including acute myocardial infarction (AMI).

Methods

A total of 90 participants were enrolled (32 with AMI, 33 with chronic stable angina; CSA, and 25 control participants) and undertook ¹⁸F-FDG PET/CT. VAT glucose uptake was measured by using maximum standardized uptake value (SUVmax) of VAT region. The target-to-background ratio (TBR) of carotid artery was defined as the SUVmax of carotid artery divided by the SUVmax of jugular vein. The SUVmax of spleen, bone-marrow (BM), and high-sensitivity C-reactive protein (hsCRP) were used for the assessment of systemic inflammatory activity.

Results

VAT SUVmax was highest in participants with AMI, intermediate in participants with CSA, and lowest in control participants. Carotid artery TBR and systemic inflammatory surrogate markers including spleen SUVmax, BM SUVmax, and hsCRP were also higher in the AMI group than in the CSA or control group. Furthermore, VAT SUVmax showed significant positive correlation with carotid artery TBR, spleen SUVmax, BM SUVmax, and hsCRP. In multivariate linear regression and logistic regression analyses, VAT SUVmax was independently associated with carotid artery TBR and AMI.

Conclusions

Glucose uptake of VAT assessed by ¹⁸F-FDG PET/CT was associated with the severity of CAD and synchronized with the carotid artery inflammation in participants with CAD.

Rapid reduction in plaque inflammation by sonodynamic therapy inpatients with symptomatic femoropopliteal peripheral artery disease:A randomized controlled trial

BACKGROUND

Inflammation is actively involved in the clinical manifestation of peripheral artery disease (PAD). Sonodynamic therapy (SDT), a novel non-invasive, plaque-based, macrophage-targeted anti-inflammatory regimen for atherosclerosis has the potential to improve walking performance by reducing plaque inflammation.

METHODS

This phase-2, randomized, sham-controlled, double-blind clinical trial enrolled 32 participants with symptomatic femoropopliteal PAD. The primary outcome was the 30-day change in the target-to-background ratio (TBR) within the most diseased segment (MDS) of the femoropopliteal artery assessed through positron emission tomography/computed tomography (PET/CT). The secondary outcomes were changes in walking performance, limb perfusion, lesional morphology and quality of life measurements.

RESULTS

The mean age was 64.7 years and 63% were male. Thirty-one completed follow-up. SDT significantly decreased the MDS TBR by 0.53 (95% CI, -0.70 to -0.36, P < 0.001) compared with control. Furthermore, SDT increased peak walking time by 118.6 s (95% CI, 74.3 to 163.0, P < 0.001), increased ankle-brachial index by 0.11 (95% CI, 0.07 to 0.14, P < 0.001), decreased lesional diameter and area stenosis by 7.2% (95% CI, -8.6 to -4.5, P < 0.001) and 9.6% (95% CI, -24.5 to -5.3, P = 0.005), respectively, and increased the walking speed score of the Walking Impairment Questionnaire by 16.1 (95% CI, 2.6 to 29.5, P = 0.021) and the physical functioning score of the 36-item Short-Form Health Survey by 10.0 (95% CI, 5.0 to 20.0, P = 0.003) compared with control. These improvements were maintained in the SDT group up to 6-month.

CONCLUSIONS

SDT rapidly reduced plaque inflammation and improved walking performance among patients with symptomatic PAD.

TRIAL REGISTRATION

Clinical Trials NCT03457662.

Analysis of 18F-Fluorodeoxyglucose and 18F-Fluoride Positron Emission Tomography in Korean Stroke Patients with Carotid Atherosclerosis

Objective

The objective of this study was to analyze uptake patterns and intensity of ¹⁸F-fluorodeoxyglucose (FDG) and ¹⁸F-sodium fluoride (NaF) radioligands in carotid atheroma among stroke patients according to carotid atheroma characteristics.

Methods

Between September 2015 and January 2017, consecutive acute stroke or transient ischemic attack patients with 50% or more proximal internal carotid artery stenosis on brain computed tomography angiography were prospectively enrolled. All patients received FDG and NaF positron emission tomography (PET) evaluation when their neurological status was stabilized. Uptake values of FDG and NaF were compared by target to blood ratio (TBR) according to the calcification burden, atheroma volume and the presence of a necrotic core of carotid atheroma.

Results

A total of 18 patients with 36 carotid arteries were finally enrolled, with 10 patients diagnosed as acute cerebral infarction due to symptomatic carotid stenosis. FDG uptake at symptomatic carotid arteries was significantly more increased than that at asymptomatic arteries (TBR: 1.17±0.23 vs. 1.01±0.15, Mann-Whitney U-test, p=0.02), but NaF uptake was not different (TBR: 1.38±0.49 vs. 1.51±0.40, p=0.40). In terms of calcification degree, NaF uptake increased as calcification burden increased (none, 1.28±0.36; spotty, 1.29±0.29; linear, 1.74±0.44; analysis of variance, p=0.02).

Conclusion

Carotid evaluation by FDG is superior to NaF PET in the detection of symptomatic carotid atherosclerosis among stroke patients. NaF PET uptake reflects the overall calcification burden.

Novel Positron Emission Tomography Tracers for Imaging Vascular Inflammation

Purpose of Review

To provide a focused update on recent advances in positron emission tomography (PET) imaging in vascular inflammatory diseases and consider future directions in the field.

Recent Findings

While PET imaging with ¹⁸F-fluorodeoxyglucose (FDG) can provide a useful marker of disease activity in several vascular inflammatory diseases, including atherosclerosis and large-vessel vasculitis, this tracer lacks inflammatory cell specificity and is not a practical solution for imaging the coronary vasculature because of avid background myocardial signal. To overcome these limitations, research is ongoing to identify novel PET tracers that can more accurately track individual components of vascular immune responses. Use of these novel PET tracers could lead to a better understanding of underlying disease mechanisms and help inform the identification and stratification of patients for newly emerging immune-modulatory therapies.

Summary

Future research is needed to realise the true clinical translational value of PET imaging in vascular inflammatory diseases.

Immunometabolism and atherosclerosis: perspectives and clinical significance: a position paper from the Working Group on Atherosclerosis and Vascular Biology of the European Society of Cardiology

Inflammation is an important driver of atherosclerosis, and the favourable outcomes of the Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS) trial revealed the large potential of anti-inflammatory drugs for the treatment of cardiovascular disease, especially in patients with a pro-inflammatory constitution. However, the complex immune reactions driving inflammation in the vascular wall in response to an atherosclerotic microenvironment are still being unravelled. Novel insights into the cellular processes driving immunity and inflammation revealed that alterations in intracellular metabolic pathways are strong drivers of survival, growth, and function of immune cells. Therefore, this position paper presents a brief overview of the recent developments in the immunometabolism field, focusing on its role in atherosclerosis. We will also highlight the potential impact of immunometabolic markers and targets in clinical cardiovascular medicine.

Synthesis and Evaluation of 11C- and 18F-Labeled SOAT1 Inhibitors as Macrophage Foam Cell Imaging Agents

PD-132301, an inhibitor of sterol O-acyltransferase 1 (SOAT1; also known as acyl-coenzyme A:cholesterol acyltransferase-1, ACAT1), is under clinical investigation for numerous adrenal disorders. Radiolabeled SOAT1 inhibitors could support drug discovery and help diagnose SOAT1-related disorders, such as atherosclerosis. We synthesized two radiolabeled SOAT1 inhibitors, [11C]PD-132301 and fluorine analogue [18F]1. Rat biodistribution studies were conducted with both agents and, as the most selective tracer, [11C]PD-132301 was advanced to preclinical positron emission tomography studies in (atherosclerotic) ApoE-/- mice. The uptake of [11C]PD-132301 in SOAT1-rich tissue warrants further investigation into the compound as an atherosclerosis and adrenal imaging agent.

Stress-Associated Neurobiological Pathway Linking Socioeconomic Disparities to Cardiovascular Disease

BACKGROUND

Lower socioeconomic status (SES) associates with a higher risk of major adverse cardiac events (MACE) via mechanisms that are not well understood.

OBJECTIVES

Because psychosocial stress is more prevalent among those with low SES, this study tested the hypothesis that stress-associated neurobiological pathways involving up-regulated inflammation in part mediate the link between lower SES and MACE.

METHODS

A total of 509 individuals, median age 55 years (interquartile range: 45 to 66 years), underwent clinically indicated whole-body ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography imaging and met pre-defined inclusion criteria, including absence of known cardiovascular disease or active cancer. Baseline hematopoietic tissue activity, arterial inflammation, and in a subset of 289, resting amygdalar metabolism (a measure of stress-associated neural activity) were quantified using validated ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography methods. SES was captured by neighborhood SES factors (e.g., median household income and crime). MACE within 5 years of imaging was adjudicated.

RESULTS

Over a median 4.0 years, 40 individuals experienced MACE. Baseline income inversely associated with amygdalar activity (standardized β: -0.157 [95% confidence interval (CI): -0.266 to -0.041]; p = 0.007) and arterial inflammation (β: -0.10 [95% CI: -0.18 to -0.14]; p = 0.022). Further, income associated with subsequent MACE (standardized hazard ratio: 0.67 [95% CI: 0.47 to 0.96]; p = 0.029) after multivariable adjustments. Mediation analysis demonstrated that the path of: ↓ neighborhood income to ↑ amygdalar activity to ↑ bone marrow activity to ↑ arterial inflammation to ↑ MACE was significant (β: -0.01 [95% CI: -0.06 to -0.001]; p < 0.05).

CONCLUSIONS

Lower SES: 1) associates with higher amygdalar activity; and 2) independently predicts MACE via a serial pathway that includes higher amygdalar activity, bone marrow activity, and arterial inflammation. These findings illuminate a stress-associated neurobiological mechanism by which SES disparities may potentiate adverse health outcomes.

Whole-Body Atherosclerosis Imaging by Positron Emission Tomography/Magnetic Resonance Imaging: From Mice to Nonhuman Primates

Cardiovascular disease due to atherosclerosis is still the main cause of morbidity and mortality worldwide. This disease is a complex systemic disorder arising from a network of pathological processes within the arterial vessel wall, and, outside of the vasculature, in the hematopoietic system and organs involved in metabolism. Recent years have seen tremendous efforts in the development and validation of quantitative imaging technologies for the noninvasive evaluation of patients with atherosclerotic cardiovascular disease. Specifically, the advent of combined positron emission tomography and magnetic resonance imaging scanners has opened new exciting opportunities in cardiovascular imaging. In this review, we will describe how combined positron emission tomography/magnetic resonance imaging scanners can be leveraged to evaluate atherosclerotic cardiovascular disease at the whole-body level, with specific focus on preclinical animal models of disease, from mouse to nonhuman primates. We will broadly describe 3 major areas of application: (1) vascular imaging, for advanced atherosclerotic plaque phenotyping and evaluation of novel imaging tracers or therapeutic interventions; (2) assessment of the ischemic heart and brain; and (3) whole-body imaging of the hematopoietic system. Finally, we will provide insights on potential novel technical developments which may further increase the relevance of integrated positron emission tomography/magnetic resonance imaging in preclinical atherosclerosis studies.

PET Scan with Fludeoxyglucose/Computed Tomography in Low-Grade Vascular Inflammation

Fluorodeoxyglucose-PET/computed tomography combines the high sensitivity of PET with the excellent spatial resolution provided by computed tomography, making it a potentially powerful tool for capturing and quantifying early vascular diseases. Patients with chronic inflammatory states have an increased risk of cardiovascular events; there is also increased vascular fluorodeoxyglucose uptake seen compared with healthy controls. This review examines the use of fluorodeoxyglucose-PET/computed tomography in assessing low-grade vascular inflammation in chronic inflammation and then reviews fluorodeoxyglucose-PET/computed tomography as a tool in monitoring the efficacy of various treatments known to modulate cardiovascular disease.